(1) Field of the Invention
The invention relates to local hyperthermia therapies.
(2) Description of Related Art
Local hyperthermia therapies are techniques that are commonly used to locally treat biological tissues. They consist in heating a target zone of the biological tissue using an energy source (laser, microwave, radiofrequency wave, ultrasound, etc.).
These techniques offer numerous advantages. From the qualitative viewpoint, they offer a great deal of potential for controlling treatments such as gene therapy, the localized application of drugs, the ablation of tumours, etc. From an economic viewpoint, they are compatible with ambulatory treatment of the sick and therefore make it possible to reduce the hospitalization time.
In general, local hyperthermia therapies allow medical interventions the invasive nature of which is reduced to a minimum.
Among the types of energy used, focused ultrasound (FUS) is particularly advantageous because it is able to heat the focused-on zone, in a non-invasive way, deeply within the biological body, without significantly heating the tissues adjacent to the focused-on zone.
During treatment, the temperature of the target zone and of its immediate surroundings needs to be controlled precisely and continuously, although the supply of energy is localized and fast (of the order of a few seconds). U.S.Pat. No. FR 2 798 296 filed on Sep. 13, 1999 in the name of the Centre National de la Recherche Scientifique (CNRS) describes an assembly for the heat treatment of biological tissues. The assembly described in that document takes account of the actual spatial distribution of temperature in the target zone and in its immediate surroundings. This spatial distribution makes it possible to estimate precisely how much energy needs to be applied and to influence the energy source accordingly. Such an assembly makes it possible both quickly to obtain the desired temperature in the target zone and to maintain and control the temperature in this target zone with increased precision, by comparison with that which was possible with earlier techniques.
The disadvantage with this assembly is that it is based on a model of a heated region that is very localized in space. In consequence, it allows control over the change in temperature in the target zone but does not allow control over the temperature distribution when several energy sources are used or when the energy is applied simultaneously to several places, for example using an array of emitters.